This invention relates generally to open-end spinning machines and, more particularly, to a method of producing electroplated combing rollers employed in spinning units of the open-end spinning machine.
In an open-end spinning machine including a succession of spinning units, a combing roller with fiber-gripping means is employed in each spinning unit to open up a sliver into individual fibers. The fiber-gripping means comprise a metallic wire with a fiber-gripping surface consisting of a plurality of spaced needles or spikes, which undergo strong friction during the combing-out operation due to contacts with the fibers and will become worn away. The friction which is generated is very strong, especially when the slivers undergoing this operation are synthetic materials. Therefore, in order to restrain the abrasion which the fiber-gripping surface must undergo, and to improve the effective life of the entire fiber-gripping means, the fiber-gripping surface must be provided with some wear-resistant layer. In a carding machine, this wear-resistant layer normally consists of a layer of hardened chromium and it has not been found that a similar layer can be provided in an open spinning machine, because it exhibits a good wear-proof property and can be obtained at a low manufacturing cost. At the same time, the fiber-gripping means itself is formed from carbon steel because it has been found to provide the highest physical strength against the pulling forces of the fibers.
With respect to the cylindrical body which forms the basic constructional element of the combing roller in which the fiber-gripping means are mounted spirally, the combing roller is made of light aluminum alloy which, because of its lightness, helps to save in the overall total power consumption which is required to operate the open-end spinning machine.
Since the combing roller must necessarily be at a relatively small diameter (50-60 mm), this makes it very difficult to wind a previously hardened, chromium plated fiber-gripping means around the cylindrical body without cracking or breaking the chromium plated layer. Of course, a cracked or broken layer of chromium would seriously hamper the effective operation of the combing roller. Therefore, it would be preferable to have a fiber-gripping means of carbon steel which has not been previously plated or coated with chromium wound around the aluminum cylindrical body of the combing roller and fitted into the recesses therein, and thereafter have a hardened chromium layer electroplated to both the aluminum cylindrical body and the steel fiber-gripping means simultaneously.
The inventors of the present invention, however, encountered many difficulties when trying to electroplate both the steel fiber-gripping means and aluminum cylindrical body with hardened chromium at the same time and under the same conditions. Specifically, in the case of hardened chromium, it is very difficult to provide a uniform deposition thereof on a cathode in an electroplating process since the thickness of the hardened chromium deposit is greatly influenced by the magnitude of current density, and, as a result, it is very difficult to obtain good adherence of the hardened chromium to the aluminum, since the aluminum may easily have thereon an oxide film which, in electroplating, prevents the formation of deposit nuclei thereon. It is, therefore, understood that when the plating is effected after the mounting of the fiber-gripping means around the cylinder, the hardened chromium layer formed on the cylindrical aluminum alloy body tends to be incomplete; this can cause problems. Incompleteness causes the portions of chromium on the aluminum body to peel away during the combing out operation due to the great stress which the body must undergo, and therefore the fibers being separated are caught by the poorly plated portions of chromium and, as a result, the yarn may break or the yarn quality will be greatly lowered.
Since it is still necessary to coat the wires but not the aluminum cylindrical body, attempts have been made at masking the aluminum cylindrical body during the time the wires wound therearound are plated. Masking the aluminum cylindrical body, while leaving the wires extending thereabove free to receive the chromium plate, however, is no simple task. The mask must be essentially very narrow to fit between the wound metallic wires and must be carefully positioned between the wires. Due to the small sizes which are involved, this masking technique is very expensive because of the detailed work which is required.